Climate Change, Global Warming and Water-Vapour

As the quantum of water vapour remains projected to rise as a result of anthropogenic GHG-induced warming; and with reference to the trends in global water vapour (that remains connected to the global energy budget and hydrological cycle) using satellite measurements, even though, water vapour kept increasing significantly in Greenland (4 to 5% per annum) and part of Europe (1 to 2% per annum) for the period between 1996 and 2006, why did water vapour decline in the Northwest United States (−1 to −2% per annum) as well as Amazonia and central Africa (approximately −1% per annum) – during the same period?

In the absence of precisely quantifying the role of the feedback mechanisms in the climate system that includes water vapour as well, would it remain feasible to deduce an accurate amount of global warming caused by the rise in GHGs in the atmosphere?

Are we sure that the water vapour feedback amplifies externally imposed climate changes [enhancement in GHGs], to the same extent as it amplifies internally generated climate variations?

With water vapour variability in the tropics remains strongly affected by ENSO and PDO, while, the same gets affected by SHSIE and NHSIE in the southern and northern hemispheres respectively; do we still have ‘clear’ seasonal variability in the tropics?

With an increase in global tropospheric water vapour of around 0.01 - 0.1 kg/m2/year, can any region on the earth could lead to an increase in regional temperature through radiative effects that could exceed -100 W/m2 at the surface?

Whether the currently pronounced positive feedback mechanism (where, the rise in temperature, from climate change leads to an increase in evapotranspiration, which again leads to an increase in the amount of atmospheric water vapour) would get terminated abruptly upon stop emitting CO2?

Suresh Kumar Govindarajan

Professor [HAG]

IIT Madras, 23-Dec-2024